1. Field of the Invention
This invention relates generally to a waveguide transition structure and, more particularly, to a waveguide transition probe for coupling a millimeter wave electromagnetic signal from a dielectric loaded waveguide to a coaxial connection.
2. Discussion of the Related Art
State of the art communication systems, such as radar systems, satellite communication systems, etc., that operate in millimeter wave frequencies (20 GHz-300 GHz), generally include an antenna that collects the millimeter wave radiation from air for reception purposes, and some type of millimeter wave integrated circuit (MMIC) that detects and processes the millimeter wave radiation collected by the antenna. The MMIC would include various components, such as amplifiers, diode detectors, filters, etc., depending on the particular application of the system, as would be known to those skilled in the art.
Waveguides are typically provided to direct the millimeter wave radiation collected by the antenna to the MMIC. The millimeter wave radiation generally travels in air through the waveguide, and is collected by a coaxial connection that is electrically connected to the MMIC. The waveguide and the MMIC are generally much different in size, and thus the waveguide will include transitions to reduce its size from the antenna to the coaxial connection. The various transitions through the waveguide, including the transition from the air waveguide to the coaxial connection, are such that the transitions are impedance matched to limit the losses of the collected radiation to a minimum. Because the MMIC is usually a very small component and the antenna is relatively larger for millimeter wave applications, the transition to the coaxial connection suitable for the MMIC without significant loss is difficult to obtain.
Waveguide to coax transitions are known in the art, where the waveguide is a thin rectangular member having conductive surfaces, and the coax includes an inner pin conductor and an outer conductor. In the known transition schemes from waveguide to the coax, the outer conductor is electrically connected to one conductive surface of the waveguide, and the inner conductor extends into a dielectric medium within the waveguide and contacts an opposite conductive surface. The electromagnetic waves that make up the millimeter wave radiation impinge the inner conductor and induce a current that is directed to the MMIC. Typically, the coax connections to the waveguides in the prior art are considerably larger than the MMICs to provide a suitable connection with minimal losses. Improvements can be made to reduce the size of the coax connection to the waveguide to make it more effective to be connected to the MMIC.
What is needed is a waveguide to coax transition scheme that is effective in reducing or minimizing electrical losses, can be produced at a low cost, and has a size compatible with the state of the art MMIC technology. It is therefore an object of the present invention to provide such a transition.